Method of manufacturing glass syringes with interchangeable pistons and barrels



June 9, 1953 s. KOLODNY EIAL 2,641,093 METHOD OF MANUFACTURING GLASSSYRINGES WITH INTERCHANGEABLE PISTONS AND BARRELS Original Filed May 25,1950 FIG.1

F I G. 2

IIIIJIIIIIJJIIIMIIIIIIIIIIIIlllllllll Mckolas fgueger Mc/(o/as JV/zccz'& Samuel fL 0Z0dz2y INVENTORS BY v r ATTORNEY Patented June 9, 1953UNITED STATES PATENT OFFICE METHOD OF MANUFACTURING GLASS SYRINGES WITHINTEROHANGEABLE PISTONS AND BARRELS ration of New Jersey Originalapplication May .25, 1950, Serial No. 164,138. Divided and thisapplication July 5, 1951, Serial No. 235,264

2 Claims.

This invention relates to glass hypodermic syringes and, moreparticularly, to novel syrmges of this type in which the pistons andbarrels of syringes of a given cubic capacity may be readilyinterchanged Without loss of effective pumping power. This applicationis a division of our copending application Serial No. 164,138, filed May25, 1950.

In the present manufacture of glass hypodermic syringes, each pistonmust be carefully finished to match a particular barrel. When somatched, the mating piston and barrel are marked with identicalidentifying serial numbers so that, thereafter, each piston can beassembled with its mating barrel. Except by remote chance, no pistonwill have a pressure-tight fit with any barrel other than the one it hasbeen finished to fit,

These syringes, after assembly, are required to pass a test in which thesyringe must retain from 20 to 70 lbs/sq. in. pressure, depending onsize, for at least 30 seconds. This test requires a substantiallyhermetic seal between the cylindrical surface of the piston and theinner cylindrical surface of the barrel chamber. As the barrel chambers,when ground to insure linearity and axial alignment, are of differinginternal diameters, each barrel must have a piston carefully finished tomatch its chamber.

This has many advantages, such as the necessity, during manufacture, ofassembling the syringe and measuring its capacity before the capacitygraduations are individually applied to the barrel surface. Furthermore,when a group of syringes are disassembled for sterilizing for example,matching of the correspondingly numbered barrels and pistons is a timeconsuming and exacting operation. When a piston is broken, for example,its mating barrel becomes useless and is usually discarded.

In accordance with the present invention, it has been found that thesedisadvantages can be eliminated by finishing all pistons, for syringesof one capacity, to a predetermined standardized dimension, andcorrespondingly finishing all barrels of such capacity syringes to amating standardized dimension. While attempts have hitherto been made toprovide glass hypodermic syringes with interchangeable pistons andbarrels, they have been unsuccessful. With the present invention, in agroup of syringes of equal capacity, any piston can be used with anybarrel and fully meet the above-mentioned pressure test.

The invention involves the grinding of the piston, on a centerlessgrinder, to a predetermined diameter, after which the piston is lappedwith an optical powder in a chemical and/or oil solution to a finish ofi0.0001" relative to such dimension (herein termed X) The barrelchambers are likewise ground to dimension X, which is dependent upon thesyringe capacity, and then lapped with a diamond solution to a toleranceof 0.0001" relative to X. When so finished any barrel assembled with anypiston will meet the pressure test.

For an understanding of the invention principles, reference is made tothe following description and the accompanying drawing. In the drawing:

Fig. 1 is an elevation view of a prior art glass hypodermic syringe.

Fig. 2 is a corresponding elevation view of the invention syringe.

Fig. 3 is an elevation view of the piston.

Fig. 4 is an axial sectional View of the barrel.

Referring to Fig. 1, which illustrates a glass hypodermic syringe I!) ofthe present type, the barrel II and piston 12 thereof are notinterchangeable. Consequently, the barrel and piston carry matchingserial numbers, indicated at I3 and It, so that, after disassembly forcleaning or the like, the piston II can be reassembled with its uniquelymatching barrel 10.

One of the requirements of such a glass hypodermic syringe is that,under test, with the passage ll of nipple it closed, the chamber I8 ofbarrel ll, having its outer end closed by piston I2, hold a pressure of'70 pounds per square inch for 30 seconds. This requires a very close,ground fit between the outer surface of piston l2 and the surface ofchamber 18, as well as exact axial alignment thereof.

In the usual manufacture of glass syringes, the barrel and piston areformed, the barrel surfaces are ground to assure true axial alignmentthroughout the length of chamber l8, and then a piston is ground toprovide a tight-fit within a particular barrel, as well as to assureaxial alignment of the piston surface. When a, particular barrel and aparticular piston have been so mated as to have a fit tight enough tomeet the above pressure test, they are then marked with identical serialnumbers. Thi assures each piston being always assembled with its ownmatched barrel.

This arrangement has many disadvantages. For example, should either thepiston or barrel of av particular syringe be broken, the unbrokensyringe member must be discarded. It is only by a remote chance that anunbroken piston, for example, could possibly match another barrel,

and trying to find such a match would be a tedious procedure without anycertainty of ultimate success.

Additionally, the graduation markings on the surface of the barrel canbe placed thereon only after the barrel and piston have been properlyfinished to the required tightfit. "The capacity of the barrel is thenaccurately 'measured and the graduations applied. This requiresindividual measurement and markingof each syringe, a costly and timeconsuming process.

These glass syringes are used in-large quantitles in hospitals, forexample, and after .each use, the syringes must be disassembled forsterilization. Usually, a large number of syringes are sterilized at thesame time. After'sterilization, each syringe barrel must be reassembledwith its mating piston. This requires a selection of a particularbarrel, for examplaand .a time consuming search for its correspondinglynumbered piston. The operation is further complicated by .the fact thatthe sterilized elements must be handled by tweezers, thus fur- .therlengthening the time required in sorting and assembling.

The present invention obviates the foregoing disadvantages by providingglass syringes in which the barrels and pistons are mutuallinterchangeable and any piston has a tight enough fit in any barrel tomeet the pressure test of holding 20 to '70 lbs/sq. in. for 30 seconds.Re- .ferring to Fig. 2, it will be noted that the barrel 2| and piston22 of the invention syringe .20 are characterized by'the lack ofmatchingidentification serial numbers.

In the manufacture of syringe 20, piston 2| (Fig. 3) is ground on acenterless grinder to assure linearity and axial alignment. The pistonsurface 3| is then lapped with a fine optical grinding powder suspendedin a suitable .solution of chemicals and/or oils. Precision gauges areused to position and check the piston during the grinding and lapping.

The piston is thus finished to a tolerance of 100001 with respect to thedimension required for a given capacity syringe, this dimension beingdenoted X in Fig. 3. As known .to those skilledin the art,glasshypodermic syringes. are standardized as to capacity as measured incubic centimeters (00.), the standard sizes generally I being 1, 2, 5,10, 20, 30, 50 and 100 cc. The

.most common sizes are 2, 5, 10 and 20 cc.

The barrel 2| has the surface of chamber v28 ground, as on a centerlessgrinder, to insure .llnearity and axial alignment.

chamber 23 is then lapped, with a diamond solution, for example, to therequired dimension K (Fig. 4) with a tolerance of 0.0001, the

When a group of barrels and a group of pistons have been finished inaccordance with the .invention procedure, any piston can be inserted .inany barrel and the assembly will meet the test of .holding 20 to .70lbs/sq. in. for .30 seconds. When disassembled, there is no need toassemble any particular piston with a selected barrel, thus eliminatingthe tedious sorting and matching procedure hitherto necessary. Shouldeither a barrel *or a piston be broken, 'theunbroken piston or barrelcan be 'assembled'with The surface .of z

any other barrel or piston, respectively, eliminating wastage ofunbroken elements. A further feature is that the graduation marks can beuniformly applied to all barrels of the same capacity, no specialmeasuring and application technique being required. Of course, eachpiston fits only the barrels of a given capacity syringe. For example,the piston of a 5 cc.

it should beunderstood that the invention may be otherwise embodiedwithout departing from such .principles.

.What is claimed'is:

1. The method of manufacturing glass hypodermic syringes, of the samecubic capacity, which comprises providing a plurality of cylindricalg-lass pistons of substantially the same diameter; precision grindingand optically lapping the surface of each piston to the samepredetermined diameter with the tolerance of the di ameter at any pointalong the linear extent thereof being 0.0001 inch; providing a plurality.of .cylindricalglass barrels of substantially the same internaldiameter; and precision grinding and optically lapping the internalsurface of each barrel to said same predetermined diameter with thetolerance of the inside diameter at any .point along the linear extentthereof being 0.0001 inch; whereby every one of said pistons willha-ve asliding sealing fit in any one .of said barrels and the respectivebarrels and pistons may be indiscriminately interchanged withoutaffecting the pressure retaining properties of the Y syringes.

2. The method of manufacturing glass hypodermic syringes, of the samecubic capacity, which comprises providing a'plurality of cylindricalglasspistonsof-substantially the same diameter; precision grinding andoptically lapping the surface of each piston to the same predetermineddiameter with the tolerance of the diameter at any point along thelinear extent thereof being 0.0001inch; providing a plurality ofcylindrical glass barrels of substantially the sameinternal diameter;precision grinding and optically lapping the internal surface of eachbarrel to said same predetermined diameter with thetolerance of theinside diameter at any point along thelinear'extent thereof being 0.0001inch;

and applying identically spaced and located capacity graduations "toeach of said barrels;

whereby every one of .said pistons will have .a

sliding sealingfitinzany .one of said barrels and the respective barrelsand pistons'ma-y be indiscriminately interchanged without afiecting thepressure retaining. properties. of the syringes.

SAMUEL KOLODNY. NICHOLAS 'MICCI. .NICHOLAS KRUEGER.

.Refercnces'Cited iILthe file of this patent UNITED STATES-PATENTS

